Circum-Mediterranean fire activity and climate changes during the mid-Holocene environmental transition (8500-2500 cal. BP)

Abstract

A mid- to late-Holocene synthesis of fire activity from the Mediterranean basin explores the linkages among fire, climate variability and seasonality through several climatic and ecological transitions. Regional fire histories were created from 36 radiocarbon-dated sedimentary charcoal records, available from the Global Charcoal Database. During the mid-Holocene 'Thermal Maximum' around 7500-4500 cal. BP, charcoal records from the northern Mediterranean suggest an increase in fire while records from the southern Mediterranean indicate a decrease associated with wetter-than-present summers. A North-South partition between 40 degrees and 43 degrees N latitude is apparent in the central and western Mediterranean. Relatively abrupt changes in fire activity are observed c. 5500-5000 cal. BP. Records of Holocene fire activity appear sensitive to both orbitally forced climate changes and shorter-lived excursions which may be related to North Atlantic cold events, possibly modulated by an NAO-like climate mechanism. In cases where human-fire interactions have been documented, the regional coherency between fire occurrence and climate forcing suggests a dominant fire-climate relationship during the early-mid Holocene. The human influence on regional fire activity became increasingly important after c. 4000-3000 cal. BP. Results also suggest that: (1) teleconnections between the Mediterranean area and other climatic regions, in particular the North Atlantic and the low latitudes monsoon areas, influenced past fire activity; (2) gradual forcing, such as changes in orbital parameters, may have triggered abrupt shifts in fire activity; (3) regional fire reconstructions contradict former notions of a gradual (mid-to late-Holocene) aridification of the entire region due to climate and/or human activities and the importance of shorter-term events; (4) Mediterranean fire activity appears hightly sensitive to climate dynamics and thus could be considerably impacted by future climate changes

Drought stress variability in ancient Near Eastern agricultural systems evidenced by δ 13 C in barley grain

“…2). We also recognize fluctuations within the sequence of the Early Bronze Age that are in line with opinions on locally variable climatic effects and settlement patterns during the Early Bronze Age (39)(40)(41)(42). During the Neolithic and Chalcolithic periods, water availability seems to have been comparatively more balanced and in agreement with other paleoclimate records (43-45), although not free of fluctuations (9).…”

Erosion in Mediterranean landscapes: Changes and future challenges

“…Natural forest fires would have been caused by lightning during "dry rainstorms", which probably occurred relatively infrequently. The frequency of such fires increased after Neolithic times and particularly from the Bronze Age, as demonstrated by Rius et al (2011) in the central French Pyrenees, and by Vannière et al (2011) for the entire Mediterranean region. Following the Bronze Age, fire frequency was driven by agro-pastoral activities and was used as an agent of landscape management.…”

“…Fires resulting from both natural and human-induced causes are a common feature of the Mediterranean region, and explain some of the main adaptative features of the Mediterranean vegetation, particularly its capacity for regeneration through survival of roots and bulbs. Lacustrine, fluvial and colluvial sediments contain charcoal and ashes from thousands of years ago, demonstrating the occurrence of natural forest fires throughout the Mediterranean (Colombaroli et al, 2009;Gil-Romera et al, 2010;Rius et al, 2011;Vannière et al, 2011;Lasheras-Álvarez et al, 2013). Natural forest fires would have been caused by lightning during "dry rainstorms", which probably occurred relatively infrequently.…”

Vegetation and fire history since the last glacial maximum in an inland area of the western Mediterranean Basin (Northern Iberian Plateau, NW Spain)

“…3500 cal yr BP; Connor et al, 2012). Furthermore, enhanced fire activity through the agency of humans was quite common from the Bronze Age onwards in the western Mediterranean Basin (Vanniere et al, 2011).…”

“…It is important to determine whether there were rapid biotic responses to these climatic changes in inland Spain, similar to those recorded in central and northern Europe Ammann et al, 2000Ammann et al, , 2012. Finally, fire history remains poorly studied in the westernmost sector of the Mediterranean Basin (e.g., Morales-Molino et al, 2011Vanniere et al, 2011;Connor et al, 2012), despite the enormous importance that fire has in the functioning of Mediterranean ecosystems (Pausas et al, 2008;Colombaroli et al, 2009;Gil-Romera et al, 2010).…”